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Glory: The Rough Road to Space

In this video from NASA, engineers describe the conditions facing the Glory spacecraft as it launches and then travels in a Sun-synchronous, low-Earth polar orbit, observing and tracking conditions on Earth. Engineering considerations include thermal stress, structural integrity, and vulnerability to vibrational effects during launch.

Some satellites orbiting the Earth peer outward into space, observing the Sun, planets, our galaxy, even distant galaxies and beyond. Some satellites, on the other hand, peer back down toward Earth. NASA’s Glory satellite was designed to orbit the Earth tracking the distribution of aerosols in the atmosphere and also measuring total solar irradiance.

Aerosols are tiny particles like dust, mist, or fumes that are suspended in air. In the atmosphere, aerosols affect how rain forms inside clouds, and they also affect how much sunlight gets reflected back into space. By tracking and measuring the distribution of atmospheric aerosols, Glory’s instruments would support and inform global climate models. Glory’s second goal - measuring solar irradiance – would help determine the Sun’s effects on Earth’s climate.

Glory’s orbital path crosses the poles in what’s called a polar orbit. Glory’s is a special class of polar orbit – a sun-synchronous orbit - that lets the satellite pass over the same part of the Earth at the same local time every day. This type of orbit allows scientists to collect and compare precisely-timed data.

Glory contains sensitive scientific instruments, but it’s also an engineering feat designed to withstand not only the strong vibrations of launch but also the extreme temperature changes it experiences in space. In its orbit, Glory cycles through day and night in very short cycles, every 100 minutes. That means Glory experiences huge temperature changes (about +/- 100 degrees C) over short periods of time. Since temperature changes affect material properties, Glory’s testing process was designed to replicate the conditions Glory would confront in space.

As heat is added to a system or absorbed by materials, the molecules that make up the material move and vibrate faster and with more energy. Thermal energy – heat – causes most materials to expand. For a satellite cycling through extreme temperatures, such fluctuations could be problematic, but NASA engineers designed Glory to maintain its structure and stability as it orbits. One way engineers can stabilize a material against thermal expansion is to make it harder and denser. With more molecules packed together more closely, a material is less likely to respond negatively to thermal fluctuations. But for objects launched into space, scientists try to minimize size, weight, and volume. So, NASA engineers had to work out creative ways to produce Glory so it’s as light and compact as possible, as strong as possible, and would withstand thermal expansion and contraction. The core of Glory is an aluminum chassis, with the whole system – including its two sensors – about the size of an oil drum. NASA engineers built on prior experience and knowledge to produce a compact, efficient satellite that can withstand the vibrations and thermal effects of launch and orbit.

Think about the hottest possible summer day and the coldest possible winter day. What happens to you when you go from one extreme to the other? What about different materials – what happens to them when they go from hot to cold, and back? What about metal? cotton? glass? How would your experience be different if you cycled through those extremes every two hours instead of over the course of a year?

What do you think are some ways we could measure how much sunlight is hitting the Earth?

Have you ever noticed that bridges sometimes include surface gaps? In the winter, those are more noticeable than in the summer. Why do you think engineers would have included those gaps in the design, and why would they be more noticeable in the winter?

While Viewing

What kinds of questions was Glory designed to help answer?

What do you think the shape of a polar orbit might be? What’s a sun-synchronous orbit?

How did NASA scientists try to replicate the conditions Glory would face in space?

After Viewing

How might Glory’s data on solar irradiance relate to climate science?

The video mentions vibrations during launch, extreme thermal cycling, and the vacuum of space. What other conditions or factors do you think would be important to consider?

Why do you think it’s important that Glory’s projected orbit was sun-synchronous?

Bonus Question: Why do you think some materials are better suited to extreme temperature changes than others? Often, engineers use composite materials for space-based hardware. Why do you think that would be the case?

The expansion and contraction of the liquid inside a thermometer demonstrates thermal expansion. Thermometers are designed to take advantage of this fact! In this exercises, students focus on the thermometer itself.

MaterialsFor each student or group of students: two thermometer (designed so the liquid expansion / contraction is obvious), two beakers, ice water, warm water

Students set up the two beakers, one with ice water and the other with warm water. They put a thermometer into each one and observe and track the movement of the liquid inside each thermometer. When the temperatures have stabilized, students switch the two thermometers and observe the reaction of each.

Discussion Questions

What would happen if the material inside the thermometers was more dense and slow to respond to thermal changes?

Was there a difference in how quickly the liquid inside the thermometers reacted when the starting state was room temperature versus when you switched the thermometers quickly between the ice water and the warm water?

Why do you think the difference in temperature would or would not make a difference in how quickly the thermometer would react?

How does this experience, which uses a liquid, relate to the video about Glory, which is a solid?

Think again about the expansion joints in bridges, roads, and tracks. Why are they designed into those systems? What would happen without them? What do those examples have in common with Glory?

Additional Activity Follow-up

Add another container of water – this one at room temperature. Students put one hand in the warm water and the other in the cold water. After they adjust to the two, students put both hands into the room temperature container. The two hands will experience the water differently based on the temperature of the previous container.

Questions: What does each hand experience? Why do you think there’s a difference? Which one is “correct?” How does this demonstration make the case for using instruments like thermometers?

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